Electrically erasable and programmable read only memories (EEPROMs) are reprogrammable nonvolatile memories that are widely used in computer systems for storing data both when power is supplied or removed. The typical data storage element of an EEPROM is a floating gate transistor, which is a field-effect transistor (FET) having an electrically isolated (floating) gate that controls electrical conduction between source and drain regions. Data is represented by charge stored on the floating gate and the resulting conductivity obtained between source/drain regions.
Increasing the storage capacity of EEPROM memories requires a reduction in the size of the floating gate transistors and other EEPROM components in order to increase the EEPROM's density. However, memory density is typically limited by a minimum lithographic feature size (F) that is imposed by lithographic processes used during fabrication. For example, the present generation of high density dynamic random access memories (DRAMs), which are capable of storing 256 Megabits of data, require an area of 8 F.sup.2 per bit of data. There is a need in the art to provide even higher density memories in order to further increase storage capacity.